Watch Art Cashin: Keep an eye on this at the close

CNBC's Mary Thompson and Art Cashin, of UBS, discuss the importance of IBM's participation in the bull run. He also says he's going to watch selling closer to the closing bell.

Art Cashin says he'll be watching to see if there's selling pressure at the close today, as there has been the rest of this week.

Cashin, UBS' director of floor operations at the NYSE, told CNBC's Mary Thompson around midday that "we've had this phenomenon now for two days where market-on-close selling shows up ... and that puts (downward) pressure (on stocks.)"